[tbb-bugs] #21388 [Applications/Tor Browser]: Tor Browser very slow/unresponsive on linux

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#21388: Tor Browser very slow/unresponsive on linux
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     Reporter:  dujaus                    |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  Medium                    |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Normal                    |   Keywords:
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
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 I know it is difficult to make quality bug reports about generic
 performance issues, but I'll try my best.

 I'm running Tor Browser 6.5 (firefox 45.7.0) on Debian 8 with 4.8 linux
 kernel from bpo. The hardware is x86_64 based laptop (3rd gen i7 CPU).

 The standard Debian firefox-esr is based on same upstream Firefox version,
 so it is easy to compare the behavior of the two browsers.

 Standard debian firefox is quite fast and responsive, even with large
 pages containing fairly heavy javascript.

 However, Tor Browser is super slow, even with javascript disabled by
 default, or browsing simple static web pages. I am not referring to
 loading pages through Tor network (it is obviously always going to be
 slower), but the GUI itself: scrolling, changing tabs, etc.

 The browser process uses very much CPU, even when there are only a few
 idle tabs open. When scrolling or typing, everything seems to stop every
 couple of seconds. Setting the security level to "low" seems to help a
 bit, but it is still way slower than the normal FF build.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21388>
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